Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 13: III-V Halbleiter II

HL 13.1: Vortrag

Freitag, 4. März 2005, 15:00–15:15, TU P-N202

Electronic structure and band alignment of GaIn(N)As/GaAs quantum wells determined by surface photovoltage and electroreflectance measurements — •M. Hetterich¹, A. Grau¹, M. Galluppi², L. Geelhaar², and H. Riechert² — ¹Institut für Angewandte Physik and Center for Functional Nanostructures (CFN), Universität Karlsruhe, D-76131 Karlsruhe, Germany — ²Infineon Technologies AG, Corporate Research Photonics, D-81730 München, Germany

GaIn(N)As/GaAs is a material system with many applications in near infrared optoelectronics. However, in particular for nitrogen-containing quantum wells (QWs) the exact band alignment and conduction band dispersion are still controversial. In this contribution we combine in a first step contactless electroreflectance (ER) spectroscopy with surface photovoltage (SPV) measurements to determine the unstrained valence band offset of GaInAs/GaAs QW structures. While ER enables sensitive measurements even of weak optical transitions between quantized electron and hole states, the advantage of SPV experiments is, that they provide a more direct access to the band offset than many other techniques. Thus, the number of free fit parameters (and their range) used in the theoretical modelling of our ER spectra can be reduced substantially, leading to better defined results. In a second step we extend our SPV studies to GaInNAs/GaAs QWs. To model the non-parabolic conduction band structure due to the presence of nitrogen we use an effective numerical procedure based on the band anti-crossing (BAC) model. Through a fit to our experimental data the band alignment as well as the BAC model parameters E_N and C_NM can be determined.